Triazolinethione-containing polymer

ABSTRACT

A poly(triazolinethione) is prepared by a process comprising the steps: 
     (a) providing a poly(acylthiosemicarbazide), 
     (b) cyclodehydrating the poly(acylthiosemicarbazide) by subjecting it to an elevated temperature in the presence of an aqueous alkaline solution to form a polyanion of a poly(triazolinethione), 
     (c) treating the polyanion of the poly(triazolinethione) with aqueous acid solution to provide the poly(triazolinethione), and 
     (d) isolating the resulting poly(triazolinethione).

FIELD OF THE INVENTION

This invention relates to a novel process for preparing polymerscontaining the [2H]-1,2,4-triazoline-3-thione ring system. In anotheraspect, it relates to polymers prepared by the process of the invention.The polymers are useful as non-migratable species in photographicconstructions.

BACKGROUND OF THE INVENTION

Photographic elements are often composed of many layers ofphotosensitive and non-photosensitive materials, with each layer makinga unique contribution to achieve a high degree of image quality. Incolor photography especially, the number of emulsion-applied layers isoften considerable, with, in addition to one or more layers beingdeposited to define the proper level for each of the primary colors,layers being present that are responsible for performing antihalation,filtering, barrier, antistatic, and antiblocking functions. These layersfunction more or less independently, and it is important that thevarious components of the layers not migrate into neighboring layers. Ifmigration occurs, the loss of the component not only diminishes overallperformance of the function for which it was added, but the migratedcomponent also can interfere with the function of neighboring layersinto which it has migrated. Migration is a serious problem inphotography, and various means have been adopted to eliminate it. Onemeans that has been utilized is to attach the migratable components in alayer to a relatively non-migratable species such as an organic polymer.

The [2H]-1,2,4-triazoline-3-thione (hereinafter referred to astriazolinethione) heterocycle, shown along with its tautomeric form(often referred to as mercapto triazole) in equation (1), is extremelyuseful in the photographic industry. ##STR1## For example, low molecularweight triazolinethione compounds have been utilized to enhance thecontrast of images in silver photography (U.S. Pat. No. 3,307,944); asagents to inhibit overdevelopment of the outermost layer of a silverhalide multilayer color construction (U.S. Pat. No. 3,615,522); asanti-bronzing agents to maintain a high degree of image intensity andcontrast (U.S. Pat. No. 3,647,451); as stabilizers for developed images(U.S. Pat. No. 3,718,468); and as photosensitive agents for maintainingimage contrast (U.S. Pat. No. 3,832,186). All these utilizations haveinvolved relatively migratable, low molecular weight, i.e., of 200 orless, compounds.

In two instances the triazolinethione heterocycle has been incorporatedinto monomers which then undergo polymerization to afford heterocyclicpolymers. An isopropenyl-functional monomer 1 (as described by Cr.Simionescu, et al., Acta Chim. Acad. Sci. Hung., 86, 459 (1975); ChemAbstr., 84, 44710v (1976)) was free-radically polymerized; the purposeof forming the polymer was not divulged. ##STR2## Bis(epoxide) monomer 2was also disclosed (O. P. Shvaika, et al., USSR 765,267 (1978); Chem.Abstr., 94, 104319t (1981)) for use in epoxy resins to reduce theself-hardening temperature. ##STR3## In a third instance, M. I.Shtil'man, et al., Polymer Sci. USSR, 10, 2827 (1969), disclose asolventless, thermal cyclodehydration of one particularpoly(acylthiosemicarbazide) 3 to form apoly([2H]-1,2,4-triazoline-3-thione) 4 according to equation (2).##STR4##

We have examined the above cyclodehydration with otherpoly(acylthiosemicarbazides), however, and have found that oftencrosslinked poly(triazolinethiones) which are insoluble and intractableare the result.

SUMMARY OF THE INVENTION

Briefly, the present invention provides a process for preparing apoly(triazolinethione) compound comprising the steps:

(a) providing a poly(acylthiosemicarbazide),

(b) cyclodehydrating the poly(acylthiosemicarbazide) by subjecting it toan elevated temperature in the presence of an aqueous alkaline solutionto form a polyanion of the poly(triazolinethione),

(c) treating the polyanion of the poly(triazolinethione) with aqueousacid to provide the poly(triazolinethione), and

(d) isolating the resulting poly(triazolinethione).

The present invention provides an improved process for preparingpoly(triazolinethiones) by cyclodehydration ofpoly(acylthiosemicarbazides), the improvement being utilization ofmoderately elevated temperatures and an aqueous alkaline solution toeffect cyclization, followed by treatment with acid to form thepoly(triazolinethione) structure.

In another aspect, poly(triazolinethiones) prepared by the novel processof the present invention are disclosed. The poly(triazolinethiones) ofthe invention remain soluble in polar organic solvents such asdimethylsulfoxide (DMSO), dimethylformamide (DMF), N-methylpyrrolidone(NMP), and dimethylacetamide (DMA), and can be efficiently fabricatedinto the final application configuration, such as a thin layer orcoating, by conventional methods such as solution and melt processing.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a novel process for the cyclodehydrationof poly(acylthiosemicarbazides) to poly(triazolinethiones). The instantprocess provides a marked improvement over prior art thermalcyclodehydrations in that poly(triazolinethione) polymers that aresoluble in polar organic solvents are the result. By soluble in polarorganic solvents is meant that at least 0.1 weight percent dissolves ina solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, or N-methylpyrrolidone at about 23° C. The polymers cancontain in the range of 2 to 10,000, and preferably 5 to 5,000,triazolinethione units. In contrast, application of the thermalcyclodehydrative method disclosed by M. I. Shtil'man, et al., discussedabove, often leads to crosslinking and insolubilization, which are notdesirable because it is then impossible to either coat a solution of thepoly(triazolinethione) or to thermally manipulate the polymer into thedesired end-use configuration.

The novel process of the present invention consists of the followingsteps:

STEP (a)

The poly(acylthiosemicarbazides), which are precursors to the desiredpoly(triazolinethiones), are known in the art and are convenientlyprepared as outlined by M. I. Shtil'man, et al., Polymer Sci. USSR, 10,2827 (1969). They are the reaction products of bis(isothiocyanates)(Formula I below) and bis(hydrazides) (Formula II below) as illustratedin Equation (3): ##STR5## wherein the bridging groups X and Y can be anydivalent organic group such as alkylene groups having from 2 to 20carbon atoms and arylene groups having from 6 to 20 carbon atoms and,optionally, can be interrupted by one to five catenary heteroatoms ofoxygen, nitrogen, silicon, or sulfur (each heteroatom being separatedfrom each other by one or more carbon atoms). Further, X and Y canoptionally be substituted with groups that do not undergo reactions withthe isothiocyanate group or be chemically altered by the mild alkalinecyclodehydrative conditions of the process. Suitable substituentsinclude halo, ester, ether, silyl, nitro, and nitrile, with thehydrocarbyl groups of the substituents possessing from 1 to 4 carbonatoms.

STEP (b)

This step involves the cyclodehydration of polymers which contain two ormore acylthiosemicarbazide units, designated by Formula III in Equation(4). The cyclodehydration to form the polyanion (Formula IV), which isthe conjugate base of the poly(triazolinethione), is accomplished atmoderately elevated temperatures, i.e., 60° to 150° C., preferably 80°to 120° C., most preferably at 100° C., using a stoichiometric excess ofan aqueous alkaline solution having a pH from 8 to 13, preferably from11 to 12. The equation depicting this step is as follows: ##STR6##wherein M is a monovalent ion (e.g., an ammonium or an alkali metal ionsuch as Na⁺, K⁺, and Li⁺).

The length of time for the cyclodehydration to occur variessubstantially depending on several factors including the relativeconcentration of the acylthiosemicarbazide units in the polymer, theelevated temperature utilized, and the pH of the aqueous alkalinesolution. In most instances the reaction can be determined to becomplete when the reacting polymer, i.e., thepoly(acylthiosemicarbazide) dissolves in the aqueous alkaline solution,typically in 1 to 2 hours.

A wide variety of bases are suitable for use as aqueous alkalinesolutions in the process of the invention including ammonium salts andalkali metal (e.g., lithium, sodium, and potassium) salts of carbonates,bicarbonates, phosphates, borates, acetates, and the like. Theconcentration of the base dissolved in water is not critical so long asit is in stoichiometric excess of the acylthiosemicarbazide unitspresent. Usually, 1M solutions and volumes of 10 mL per gram ofpoly(acylthiosemicarbazide) are employed. A preferred cyclodehydrativesolution is 1M sodium carbonate. Hydroxide may be utilized as well, butonly at concentrations below about 0.1M. If the pH is greater than about13, cyclodehydration still occurs but other hydroxide-sensitive linkagesthat may also be present in the polymer such as amide, ester, and theacylthiosemicarbazide itself undergo hydrolysis reactions causing anundersirable scission of the polymer mainchain.

STEP (c)

This step involves conversion of the polyanion units (Formula V) intothe poly(triazolinethione) structure (Formula VI in Equation (5)):##STR7## This transformation is accomplished by a stoichiometric excessof an aqueous acid of pH of 6 or less, above represented by thehydronium ion (H₃ O⁺). Suitable acids include hydrochloric, nitric,sulfuric, acetic, and many others employed in at least 1 molarconcentration. This Step is particularly facile in the present inventionand generally involves simply mixing the aqueous solution containing thepolyanion and acid at room temperature.

STEP (d)

The poly(triazolinethione) polymers containing the Formula VI units areinsoluble in aqueous acid, precipitate, and can be isolated by simplefiltration or decantation of the aqueous supernatant liquid.

Bis(isothiocyanates) which are useful in the preparation of thepoly(acylthiosemicarbazides) used in Step (a) are known in the art andcan readily be prepared by reaction of diamines with thiophosgene, asexemplified by M. Uher, et al., Coll. Czech. Chem. Commun., 38, 289(1973). Bis(hydrazides) too are well known in the art and can beobtained by reaction of hydrazine and a diester, and a representativeprocedure that we have utilized has been reported by T. W. Campbell, etal., J. Appl. Polymer Sci., 2, 155 (1959).

Polymerization of the bis(isothiocyanate) with the bis(hydrazide) canconveniently be conducted by heating from 80° to 150° C., preferablyfrom 100° to 140° C., over the course of 1 to 6 hours, preferably from 3to 4 hours, equimolar quantities of the two monomers inN,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) solution. Thesetwo solvents are generally preferred because the monomers and resultantpolymers are soluble therein, which provides a homogeneous reactionmixture over the course of polymerization. After the reaction period,the DMF or DMSO solution is cooled to room temperature and poured intoapproximately 10-fold volumes of water. The resultant precipitatedpoly(acylthiosemicarbazide) having 2 to 10,000 acylthiosemicarbazideunits, preferably 5 to 5,000 such units, is filtered and washed with anon-solvent such as ether or methanol. The polymer can be dried at thispoint, but drying is not necessary before transformation to thepoly(triazolinethione) by the novel process of the invention.

It is further contemplated as being within the scope of the presentinvention that various random copolymers can be prepared in which otherkinds of functional groups are introduced in the polymer structure thatare inert to the process conditions of our invention. Copolymerization,as is apparent to one possessing skill in the art, may be desirable incertain applications to alter specific polymer properties, e.g.,toughness, solubility, melt viscosity, and conformability, or simply tovary the concentration of the triazolinethione units within thecopolymer. The comonomers can be copolymerized in any proportion withthe bis(isothiocyanate) and the bis(hydrazide). Suitable comonomers thatmay be employed are those which are reactive, and hence copolymerizable,either with the bis(isothiocyanate) such as diamines and diols or withthe bis(hydrazide) such as diesters, diisocyanates, bis(azlactones),bis(epoxides), diacids, and diacid chlorides. Typically, thesecomonomers can simply be added to replace a portion of either thebis(isothiocyanate) or the bis(hydrazide) reactant charge.

Representative examples of useful comonomers include:

diamines:

ethylenediamine, 1,6-hexanediamine, m-xylylenediamine,1,4-diaminocyclohexane, dimerdiamine, 1,12-dodecanediamine,p-phenylenediamine, and the like;

diols:

ethyleneglycol, 1,2- or 1,3-propyleneglycol, 1,4-butanediol,1,6-hexanediol, diethyleneglycol, triethyleneglycol,1,4-cyclohexanedimethanol; polyethyleneglycol, polytetramethyleneglycol,and the like;

diacids (or their corresponding acid chlorides or lower alkyl (C₁ or C₂)esters):

adipic, azelaic, sebacic, dimer, terephthalic, and isophthalic acids,and the like;

diisocyanates:

1,6-hexanediisocyanate, toluene diisocyanate,diphenylmethanediisocyanate, isophoronediisocyanate, and the like;

epoxides:

bisphenol-A-diglycidylether and the like;

bis(azlactones):

compounds of the formula ##STR8## wherein R¹ and R² independentlyrepresent an alkyl group having 1 to 12 carbon atoms, an aryl grouphaving 6 to 12 carbon atoms, or R¹ and R² taken together with the carbonatom to which they are attached form a 5- to 12-membered carbocyclicring;

R³ is a divalent organic group having a molecular weight up to 20,000,preferably selected from a hydrocarbyl group (i.e., an alkylene grouphaving 2 to 20 carbon atoms and an arylene group having 6 to 20 carbonatoms and optionally can be interrupted by one to five catenaryheteroatoms of oxygen, nitrogen, and silicon or sulfur),polyoxyalkylene, polyester, polyolefin, polyacrylate, and polysiloxanegroups that can optionally all be further substituted by at least onenon-nucleophilic group such as cyano, halo, ester, ether, keto, nitro,silyl, or sulfide (the carbon-containing groups having up to 10 carbonatoms);

these compounds and their preparation being disclosed in Assignee'scopending patent application U.S. Ser. No. 681,553, filed Dec. 13, 1984,and incorporated herein by reference; and

a class of bis(azlactones) that can be prepared by a Michael-typeaddition of an amino or thiol group-substituted nucleophilic compound toan alkenyl azlactone and are disclosed in U.S. Pat. No. 4,485,236, andincorporated herein by reference.

Typical examples of copolymeric units that can be incorporated intocopolymers containing triazolinethione units of the invention include:

    ______________________________________                                                                   Derived by copoly-                                 Copolymeric unit                                                                           Name          merization from                                    ______________________________________                                         ##STR9##    thiourea      diamine                                             ##STR10##   thiourethane  diol                                                ##STR11##   acylhydrazide diacid derivative                                   ##STR12##   acylsemicarbazide                                                                           diisocyanate                                       ______________________________________                                    

The triazolinethione-containing polymers of the invention are useful asnon-migrating components in photosensitive materials. They can haveutility to enhance contrast, as anti-bronzing agents, as stabilizers fordeveloped images, and as antihalation agents. Thetriazolinethione-containing polymers can be included in emulsions orwith other resinous materials or can be coated out of polar organicsolvents by methods known in the art such as roll-coating, dip-coating,bar-coating, knife-coating, etc.

Having described our invention in general terms, it is now furtherdescribed by specific examples of preparations of variouspoly(triazolinethiones) by utilization of our novel process. Theparticular materials and amounts recited in the examples, however, aswell as other details and conditions, should not be construed to undulylimit the invention.

EXAMPLE 1 A. Polymerization of 1,6-bis(isothiocyanato)hexane andm-phenylene dihydrazide Step (a) ##STR13##

In a 250 mL, round-bottomed flask equipped with an argon inlet,condenser, and mechanical stirrer were placed1,6-bis(isothiocyanato)hexane (4.00 g; 20 mMol), m-phenylene dihydrazide(3.88 g; 20 mMol), and DMSO (100 mL). The solution was heated at 100° C.under an argon atmosphere for 4 hours. The solution was cooled to roomtemperature and poured with stirring into 1 L of water. The resultingwhite solid was collected by filtration and washed with methanol. Yield:7.42 grams. Spectroscopic analysis confirmed the presence of the desiredpoly(acylthiosemicarbazide).

Preparation of the poly(triazolinethione) derived from1,6-bis(isothiocyanato)hexane and m-phenylene dihydrazide Step (b)##STR14##

In a 100 mL, round-bottomed flask were placed the above preparedpoly(acylthiosemicarbazide) (5.0 grams) and 1M aqueous sodium carbonate(50 mL). The initial mixture was refluxed for 1 hour, during which timethe white solid dissolved to form a colorless solution of the polyanion.

Steps (c) and (d) ##STR15##

The aqueous alkaline solution from Step (b) was poured into a beakercontaining water (200 mL), and concentrated hydrochloric acid was addeddropwise with stirring until the pH was less than 2. The precipitatedpolymer was filtered, washed with water and methanol, and driedovernight at 50° C. under vacuum (less than 1 Torr.). Yield: 4.2 grams.Spectroscopic analysis confirmed the presence of the desiredpoly(triazolinethione).

The inherent viscosity (η) of the polymer at 30° C. in DMF (0.50 g/100mL) was 0.29 dL/g.

EXAMPLES 2-9

Using the procedure of Example 1, the various polymers shown in TABLE Iwere prepared.

                  TABLE I                                                         ______________________________________                                         ##STR16##                                                                    Example   X              Y         η.sup.(a)                              ______________________________________                                        2         (CH.sub.2).sub.6                                                                             p-C.sub.6 H.sub.4                                                                       0.27                                       3         --             (CH.sub.2).sub.4                                                                        0.31                                       4         --             CH.sub.2 OCH.sub.2                                                                      0.11                                       5         (CH.sub.2).sub.3                                                                             m-C.sub.6 H.sub.4                                                                       0.04                                       6         O(p-C.sub.6 H.sub.4).sub.2                                                                   --        0.07                                       7         p-C.sub.6 H.sub.4                                                                            --        0.15                                                  ##STR17##     --        0.22                                       9                                                                                        ##STR18##     --        0.16                                       ______________________________________                                         .sup.(a) All inherent viscosities (η, in dL/g) were measured in DMF a     in Example 1.                                                            

COMPARATIVE EXAMPLE 1

This Example teaches that thermal cyclodehydration as disclosed by M. I.Shtil'man, et al., Polymer Sci. USSR, 10, 2827 (1969) often leads toinsoluble poly(triazolinethiones).

The poly(acylthiosemicarbazide) precursor to Example 3 (2.0 grams) wasplaced in a round-bottomed flask and heated to 200° C. at less than 1Torr. for 1 hour. The resulting poly(triazolinethione) was not solublein DMF.

COMPARATIVE EXAMPLE 2

This Example teaches that the pH should be less than about 14 in orderto prevent deleterious, hydrolysis side reactions.

When step (b) of Example 1 was conducted using 1M sodium hydroxide(pH=14) instead of 1M sodium carbonate with thepoly(acylthiosemicarbazide) precursor to Example 1, no polymer wasisolated in Step (d).

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

We claim:
 1. A poly(triazolinethione) prepared by a process comprisingthe steps:(a) providing a poly(acylthiosemicarbazide), (b)cyclodehydrating said poly(acylthiosemicarbazide) by subjecting it to anelevated temperature of 60° to 150° C. in the presence of an aqueousalkaline solution to form a polyanion of a poly(triazolinethione), (c)treating said polyanion of said poly(triazolinethione) with aqueous acidsolution to provide said poly(triazolinethione), and (d) isolating saidresulting poly(triazolinethione);said poly(triazolinethione) beinguncrosslinked, and at least 0.1 weight percent of saidpoly(triazolinethione) being capable of dissolving in dimethylformamide,dimethylacetamide, dimethyl sulfoxide, or N-methylpyrrolidone at 23° C.2. A poly(triazolinethione) prepared by a process comprising thesteps:(a) providing a poly(acylthiosemicarbazide) having units of theformula ##STR19## (b) cyclodehydrating said poly(acylthiosemicarbazide)by subjecting it to a temperature in the range of 60°-150° C. in thepresence of an aqueous alkaline solution having a pH in the range of 8to 13 to form a polyanion of a poly(triazolinethione) having the unitsof the formula ##STR20## wherein M is a monovalent ion, (c) treatingsaid polyanion of said poly(triazolinethione) with an aqueous acidsolution having a pH of 6 or less to provide units of saidpoly(triazolinethione) having the formula ##STR21## and (d) isolatingand resulting poly(triazolinethione),said poly(triazolinethione) beinguncrosslinked, and at least 0.1 weight percent of saidpoly(triazolinethione) being capable of dissolving in dimethylformamide,dimethylacetamide, dimethyl sulfoxide, or N-methylpyrrolidone at 23° C.3. The poly(triazolinethione) according to claim 2 wherein saidpoly(triazolinethione) comprises in the range of 2 to 10,000triazolinethione units.
 4. The poly(triazolinethione) according to claim3 wherein said poly(triazolinethione) comprises in the range of 5 to5,000 triazolinethione units.
 5. The poly(triazolinethione) according toclaim 1 wherein said poly(acylthiosemicarbazide) of Step (a) is preparedby reacting a bis(hydrazide) compound with a bis(isothiocyanate)compound.
 6. A poly(triazolinethione) prepared by a process comprisingthe steps:(a) providing a poly(acylthiosemicarbazide) having units ofthe formula ##STR22## (b) cyclodehydrating saidpoly(acylthiosemicarbazide) by subjecting it to a temperature in therange of 60°-150° C. in the presence of an aqueous alkaline solutionhaving a pH in the range of 8 to 13 to form a polyanion of apoly(triazolinethione) having the units of the formula ##STR23## whereinM is a monovalent ion, (c) treating said polyanion of saidpoly(triazolinethione) with an aqueous acid solution having a pH of 6 orless to provide units of said poly(triazolinethione) having the formula##STR24## and its tautomeric form, and (d) isolating said resultingpoly(triazolinethione),said poly(triazolinethione) being uncrosslinked,and at least 0.1 weight percent of said poly(triazolinethione) beingcapable of dissolving in dimethylformamide, dimethylacetamide, dimethylsulfoxide, or N-methylpyrrolidone at 23° C.
 7. A poly(triazolinethione)having units of the formula ##STR25## said poly(triazolinethione) beinguncrosslinked, and at least 0.1 weight percent of saidpoly(triazolinethione) being capable of dissolving in dimethylformamide,dimethylacetamide, dimethyl sulfoxide, or N-methylpyrrolidone at 23° C.8. A process for preparing a poly(triazolinethione) comprising thesteps:(a) providing a poly(acylthiosemicarbazide), (b) cyclodehydratingsaid poly(acylthiosemicarbazide) by subjecting it to an elevatedtemperature in the presence of an aqueous alkaline solution to form apolyanion of a poly(triazolinethione), (c) treating said polyanion ofsaid poly(triazolinethione) with aqueous acid solution to provide saidpoly(triazolinethione), and (d) isolating the resultingpoly(triazolinethione).
 9. A process for preparing apoly(triazolinethione) comprising the steps:(a) providing apoly(acylthiosemicarbazide) having units of the formula ##STR26## (b)cyclodehydrating said poly(acylthiosemicarbazide) by subjecting it to atemperature in the range of 60°-150° C. in the presence of an aqueousalkaline solution having a pH in the range of 8 to 13 to form apolyanion of a poly(triazolinethione) having units of the formula##STR27## wherein M is a monovalent ion, (c) treating said polyanion ofsaid poly(triazolinethione) with an aqueous acid solution having a pH of6 or less to provide units of said poly(triazolinethione) having theformula ##STR28## (d) isolating said resulting poly(triazolinethione).10. The process according to claim 8 wherein saidpoly(acylthiosemicarbazide) is prepared by reacting a bis(hydrazide)compound with a bis(isothiocyanate) compound.